Evaluation of the Susceptibility of the Seeds of Four Varieties of Vigna unguiculata against Callosobruchus maculatus Infestations

Abstract

Introduction: Post-harvest conservation remains a major challenge for most crops in developing countries. Among these is Cowpea one of the major legumes grown and consumed in the tropics and subtropics of countries. Callosobruchus maculatus infestations constitute are the most prominent threat for this particular crop. Objective: The present research aimed at evaluating the susceptibility of four cowpea varieties against infestations of C. maculatus. Place and Duration of Study: The study was conducted at the entomology laboratory of the cowpea section of the Regional Center for Agricultural Research of Maroua from November to December 2018. Methodology: The experiments were carried out based on the factorial experiment by randomized complete design with five replications. 40 seeds of each variety were put in contact with 5 pairs of bruchids. Results: The results show that the four cowpea varieties evaluated have different physical characteristics of the seeds. This variability would play an important role in inducing the ovipositional response of C. maculatus females. However, it is not enough on its own to explain the various degree of susceptibility to C.maculatus infestations. There was a positive perfect correlation between the number of adult emergence, growth index, weight loss, number of holes and Dobie susceptibility index. Also, BR-1 was found to be more resistant to C. maculatus followed by Lori-niébé, Vya and least resistance was observed in the Borno brown. The multiple regression analysis reveals that there is a negative relationship between mortality rate of developmental stages, weight loss, F1 offspring production, and seed susceptibility. Conclusion: The physical characteristics of the four cowpea varieties tested to affect the susceptibility of the grain to beetle attacks. A number of adult emergence, growth index, weight loss, and susceptibility index are the main indicators for the resistance of cowpea to C. maculatus damage. An analysis of the amino acids contained in the BR-1 is recommended for the introgression of its resistance alleles in susceptible varieties.